Our clinical research continues to address several important aspects of the following questions: how to optimally use and administer multi-class combination anti-retroviral therapy;how to integrate immune based therapies within a framework of ongoing antiretroviral therapy;how to determine the optimal time for initiation of antiretroviral strategy in order to preserve and reconstitute immune function while at the same time minimizing long-term antiretroviral toxicities, and how to optimize the potential use of immune-based therapies as a potential means both of decreasing exposure to antiretroviral drugs and of enhancing their efficacy. A major highlight of this project has been to characterize the immunologic abnormalities associated with HIV infection, develop safe, practical immunologic approaches to the adjunctive therapy of patients with HIV infection, and utilize these immune based therapies as tools for obtaining valuable insights into the pathophysiologic mechanisms present in patients at various stages of HIV infection. One of the specific tools employed in this endeavor has been the use of subcutaneous administration of interleukin-2 (scIL-2) in order to to reverse the CD4 T cell decline associated with progressive HIV-1 infection. A series of randomized phase I-II studies were carried out that established this as a feasible method for increasing the CD4 count in patients with HIV infection;these studies were then extended to optimize the dosing regimens for maximal immunologic and virologic benefit while minimizing side effects. Intensive efforts remain underway to better characterize the function, replication, and survival of lymphocytes following both acute and chronic stimulation by IL-2 therapy. Cohorts of patients have been followed who have received IL-2 treatment for periods that now extend to almost 19 years. A major finding of these studies, elucidated using two independent means of both in vivo and ex vivo lymphocyte labeling, has been the discovery that intermittent IL-2 therapy induces a marked prolongation of the survival of CD4 T cell subsets, particularly both naive and central memory cell subsets. Extensive phenotypic study of these CD4CD25 cytokine-expanded cells (CEN) shows them to express a unique pattern of surface markers distinguishable from other CD25 populations such as T regulatory lymphocytes. The laboratory has been engaged in an extensive series of collaborations with a large number of extramural colleagues, both in the US and abroad, in the context of two major randomized phase III international clinical endpoint trials of sc IL-2. The goal of these studies was to determine whether the favorable effects of IL-2 therapy on CD4 T cell number translate into a significant delay in the onset of AIDS-defining conditions and or death in such patients versus the recipients of antiretroviral therapy alone. Data collection for these two large international trials was completed on November 15, 2008, following which both studies were subjected to multi-parameter analyses attempting to establish the correlation between cytokine-induced increases in CD4+ cell numbers and the frequency and/or severity of clinical events. Preliminary data analyses were completed in mid-January and reviewed by an international panel of site investigators and INSIGHT leadership. In brief, patients in the IL-2 arm of ESPRIT were successful in maintaining an average CD4 difference of 153 cells /uL greater than those in the ART alone arm. Patients in the IL-2 arm of SILCAAT were able to maintain an average CD4 difference of 57 cells/uL greater than those in the ART alone arm. Despite these CD4 differences between the two arms of each trial, both ESPRIT and SILCAAT were remarkably consistent in demonstrating no difference in the number of AIDS-defining events or deaths that could be ascribed to using IL-2 plus ART versus using ART alone. Based upon these two consistent findings in approximately 6000 study subjects, it was concluded that sc IL-2 therapy does not provide any clinical benefit over HAART alone in patients at either the early or advanced stages of HIV infection. Based upon informative insights gained from other large trials such as the SMART study, we are actively engaged in various subanalyses of both SILCAAT and ESPRIT in order to attempt to better understand the outcomes that were observed. For example, we are in the process of analyzing stored samples from one of these trials for the presence of elevated markers of inflammation and altered coagulation as potential predictors of differences in clinical events. As part of the conclusion of these planned investigations of IL-2 therapy, we remain the lead center in a randomized, controlled multi-center international trial designed to compare the effects of intermittent scIL-2 therapy with or without the use of peri-cycle antiretroviral treatment compared to control patients not receiving IL-2. The data generated during this multi-center trial have completed analysis and are being submitted for publication in the near future. We are also assisting in the initial preclinical testing of a novel "immuno-toxin", a monoclonal antibody linked with pseudomonas exotoxin, that may have direct antiviral activity by virtue of its affinity for HIV-infected cells. We are also fully credentialed as one of the trial sites for the "START" study (Strategic Timing of AntiRetroviral Treatment) aimed at determining whether early introduction of ART in previously-untreated patients translates into better clinical outcomes. Finally, we also continue our efforts to improve access to clinical trials by local minority populations through an outreach that includes a close relationship with local clinics for medically under-served populations.